A conventional card having a contactless interface has a large number of types, for example, ISO-18092 introduced in Non-Patent Document 1, ISO14443-B on the ISO standard introduced in Non-Patent Document 2 and a high processing IC card system (which is referred to as a “high-speed type”) defined in the Japan IC Card System Application Council (JICSAP). In recent years, there has been demanded a combination card using a plurality of different communicating methods in the contactless interface.
A contactless IC card having a plurality of communicating interface switching functions has been described in Patent Document 2 and Patent Document 3, for example.
The Patent Document 2 has disclosed a technique for detecting a time range of a logical value constituting an information signal transmitted from an external device, thereby discriminating any of a plurality of information transmitting means for transmitting the information signal together with the external device which is used by the external device on a head of the information signal and switching the information transmitting means to prevent a generation of a communication error and an extension of a communication time in a contactless electronic device loading the information transmitting means.
The Patent Document 3 has disclosed a technique for providing a single demodulator circuit capable of demodulating an input signal, a plurality of sampling circuits capable of sampling a signal output from the demodulator circuit synchronously with a predetermined clock signal, a plurality of detector circuits capable of detecting a header for each of signals output from the corresponding sampling circuits respectively, a plurality of processing circuits capable of carrying out a predetermined data processing based on a result of the detection of each of the corresponding detector circuits respectively, and a communication method deciding circuit capable of deciding any of the results of the detection of the header obtained from the detector circuits which is coincident with a preset communicating method, and for executing processings corresponding to a plurality of communicating methods which is different from each other at the same time, thereby shortening a time required for establishing a connection and actually enabling an information transfer.
A so-called IC card loading a semiconductor integrated circuit device and an antenna therein serves to exchange information between an interrogator and the semiconductor integrated circuit device and to implement various functions such as a transmission of data held by the IC card and a hold of data transmitted from the interrogator. The semiconductor integrated circuit device loaded into the IC card receives a high frequency signal supplied from the interrogator through the antenna loaded into a contactless IC card and rectifies and smoothes a voltage generated on both terminals of the antenna, thereby forming an internal voltage which is required for an operation of an internal circuit.
With advanced functions of the IC card, an operating current noise generated by a semiconductor integrated circuit device loaded into an IC card, particularly, a CPU (central processing unit) tends to be increased. The increase in the operating current noise might influence a communication in a contactless interface, thereby causing a false communication.    [Patent Document 1] JP-A-2005-222265 Publication    [Patent Document 2] JP-A-2006-072678 Publication    [Patent Document 3] JP-A-2006-060363 Publication    [Non-Patent Document 1] ISO/IEC-18092 212 kbps and 424 kbp    [Non-Patent Document 2] ISO/IEC-14443 Type-B